The extension still insert the username in thread titles for user talk pages. This is problematic because when a user is renamed the threads keep the old username instead of being renamed to the new name.

Besides, if the name of user namespace changes (as happened recently on Portuguese wikis, from "Usuário" to "Utilizador"), the threads of a user talk page will be spreaded in 3 diferent places, like

[[Special:PrefixIndex/Thread:Old Namepace:Old user name]]

and

[[Special:PrefixIndex/Thread:New Namepace:Old user name]]

and

[[Special:PrefixIndex/Thread:New Namepace:New user name]]

or

[[Special:PrefixIndex/Thread:Old Namepace:Old user name]]

and

[[Special:PrefixIndex/Thread:Old Namepace:New user name]]

and

[[Special:PrefixIndex/Thread:New Namepace:New user name]]

(In reply to comment #1)

The extension still insert the username in thread titles for user talk pages.
This is problematic because when a user is renamed the threads keep the old
username instead of being renamed to the new name.

Here is an example:
http://strategy.wikimedia.org/w/index.php?title=Special%3APrefixIndex&prefix=User+talk%3APhilippe+&namespace=90

This can be problematic when accounts are renamed for privacy reasons, because the old username will still be in the title of lots of pages (threads/replies).

This will be fixed in the LQT backend rewrite.

This seems to be still the case:

https://test2.wikipedia.org/wiki/Thread:User_talk:Qgil/Testing_bug_24240

However, this behavior is consistent with regular User_talk pages. What happenbs to those pages when a username is renamed? Do they need to rename the related Talk pages manually? And if so, couldn't be simply the same for LQT User_talk pages?

LiquidThreads has been replaced by StructuredDiscussions on all Wikimedia production wikis (except one, which will be done soon). It is no longer under active development or maintenance, so I'm re-classifying all open LQT tasks as "Lowest" priority.